1. Field of the Invention
The present invention relates to a route control technique which guarantees the validity of a route from the point of view of the management policy in the judgement whether transmitted data arrive at the destination securely or not and in the selection of a route in a network being composed of a plurality of switches (network equipment such as routers or ATM switches including networks linking to them).
2. Description of the Prior Art
With the development of computer techniques and the communication techniques, the scale of a computer network is growing larger and the configuration is also growing more and more complicated. In a network of a large scale and of a complicated configuration, the demand for the route control technique which makes it always possible to secure a proper route between a transmitter and a receiver is growing higher.
In the case of a network which is commonly used by a large number of people having a variety of demands like an Internet, the demand for the route control according to a network management policy (a predetermined rule from an operational point of view or a managerial point of view in a network, hereinafter referred to as simply a management policy) is also growing higher.
It is also made possible to separate routes for every user by the route control according to the management policy.
For a route control technique, protocols as shown in the following have been developed: the OSPF (Open Shortest Path First) and BGP-4 (Border Gate Protocol 4) by IETF (Internet Engineering Task Force), PNNI (Private Network-Network Interface) by ATM Forum, and so on. In the case of the above, respective switches perform autonomous route control, so that even in the case of a trouble in a part of switches or lines, the route control is continued by the other switches. Therefore, the above system is said to have an advantage of being strong against troubles.
However, the conventional systems have problems as shown below.
(1) A temporary line trouble
Even in a case of a change in a network configuration, a route can be held normal by the route control using the protocols mentioned in the above. For example, when a trouble occurs in a certain line or switch, a route bypassing the trouble is reset with the exchanges of route information among the switches. In the case of such a resetting, by an erroneous setting of a switch or switches, for example, such operations may occur in the network: a packet of transmission data without reaching a receiver goes round and round in the network, or the route forms a looped route. In such a case, the line trouble can be kept as it is until the error is corrected by a manager, and the influence can be serious. The setting of a switch is performed independently for every switch, so that time differences in resetting from each other may occur, which can be a cause to prevent transmitted data from being received by a receiver.
(2) Difficulty in the uniformity of management policy
In order to execute the route control in which consideration is paid to the management policy using the above-mentioned route control protocol, the management policy information is set in respective switches in the network. For example, when there are a plurality of routes for a destination, the information for judging which route is the most desirable one will be set in respective switches.
However, since the management information is set in respective switches, a route which does not satisfy the management policy intended by a network manager can be selected caused by an erroneous setting of a certain switch.
At present, as one of the purposes to solve the problems mentioned in the above (1) and (2), a route server by IETF and MPOA by ATM forum are proposed.
Both of them adopt a system in which the routes in the network are batch-processed by collecting the route information to a server called a route server which manages the route information. Therefore, a temporary line trouble as shown in item (1) due to the contradiction in route information in switches does not occur easily. Because of the centralized management of the policy information by a server, it is easy to unify the management policy not to cause the trouble as shown in item (2).
However, in the case of these server systems, there is a problem that the breakdown of a server causes the breakdown of the whole system.
An object of the present invention is to provide a network system with route verification function which prevents the occurrence of an abnormal route caused by an erroneous setting of a switch, leaving the effect of being resistant to troubles of the route control protocol system of an autonomous decentralized type, a route management apparatus, switches, and a method for operating them.
In order to achieve the above-mentioned object, the present invention provides a network system and a method of operation thereof, wherein the network system comprises a route management apparatus with a route verification means for verifying the validity of communication routes between a terminal and a switch or between switches connected to the communication network being composed of communication lines to which a plurality of switches are connected; and the above-mentioned plurality of respective switches store the route information concerning a communication route corresponding to a destination, and perform switching to output information to the communication route corresponding to the destination contained in a route information obtained by referring to the contents of the stored data, and when the above-mentioned route information is changed, they transmit a route-usage-permission-request of the route to be changed to the route management apparatus and on receiving a route-usage-permission-notice of the route to be changed sent from the route management apparatus, the stored route information is updated.
The present invention provides a communication route update system and method thereof by a route management apparatus connected to a communication network composed of communication lines to which a plurality of switches are connected and the update method of the operating system thereof, comprising storing route information for switches concerning a communication route between a terminal and a switch or between switches connected to a communication network composed of communication lines to which a plurality of switches are connected; receiving a route-usage-permission-request when the route-usage-permission-request of a communication route between a terminal and a switch or between switches connected to said communication network is transmitted from one of the plurality of switches; verifying the validity of a communication route concerning said route-usage-permission-request; a notification means for notifying one of the plurality of switches which has transmitted said route-usage-permission-request of a usage permission of a route verified by said route verification means; and an update means for updating the route information which has stored in said storage means for the route information of the communication route to which said permission notice is given.
Further, the present invention denotes a communication route update system by a switch in the communication network system composed of a plurality of switches, communication lines connected to the switches, and a route management apparatus managing the communication routes of the above-mentioned switches, and the method thereof, wherein
the switches store the route information concerning the communication route corresponding to a destination and output information to the communication route corresponding to the destination contained in the route information obtained referring to the stored information, and when one of them updates the route information, it transmits a route-usage-permission-request of a route to be changed to the route management apparatus, and on receiving the route-usage-permission-notice of the route to be changed from the route management apparatus, the stored route information is updated.
The problem (1) written in the above is caused by the fact that each switch in the network sets a route on a forwarding table independently, so that the route update in the whole network are not synchronized. Therefore, in the present invention, when the necessity a route update occurs each switch does not write the updated route information in its storage immediately, and at first, shall transmits the route information as a route-usage-permission-request to the route management apparatus by a transmission means. The route management apparatus holds the plurality of pieces of route information sent from respective switches, and verifies whether transmitted data arrive at the destination securely or not with the route verification means, and only for a route which does not form an abnormal route (a valid route), a route-usage-permission-notice is sent to the switch or switches. On receiving the route-usage-permission-notice of the route, the switch registers the route onto its storage and updates the route information. The route-usage-permission-notices of routes from the route management apparatus are transmitted to the object switches almost simultaneously. Therefore, even if the transfer delay in the network is considered, according to the present invention, synchronized route updates in the whole network are performed in a few seconds, and the verification of a route is also performed; thereby the occurrence of an abnormal route can be avoided.
The route management apparatus further comprises a notification means notifying the switch which has transmitted the usage permission request, when it is verified that the transmitted data do arrive at the destination through the route mentioned in the transmitted route-usage-permission-request, of the receipt confirmation of the route-usage-permission-request and if the respective switches, after the lapse of a predetermined period of time from the transmission of the route-usage-permission-request of the route, receive neither the receipt confirmation of a route-usage-permission-request nor the route-usage-permission-notice of the route from the route management apparatus, the stored route information concerning the route can be updated. As mentioned in the above, when it is verified that the transmitted data will not arrive at the destination, the route management apparatus notifies the switch which transmitted the route-usage-permission-request that the receipt confirmation of the route-usage-permission has been sent; thereby when the switch receives neither a receipt confirmation of a route-usage-permission-request nor a route-usage-permission-notice of the route, the switch is able to set the route information onto its storage regarding that a fault has occurred in the route management apparatus, thus the system is capable of being operated as an ordinary autonomous decentralized system, which makes it possible to avoid the breakdown of the whole network system.
In order to solve the problem (2), the route verification means can be arranged in such a manner that it verifies whether the route matches with the predetermined management policy or not. Thereby a route which is not intended to have by a manager can be prevented from being set, which is caused by an erroneous setting of the management policy information in a switch, etc.
When the route verification means in a route management apparatus holds a route information which is verified that the transmitted data do not arrive at the destination, for a predetermined period of time, if the apparatus further comprises an output means to output the information of such a state as mentioned in the above to an external circuit, it is able to notify a manager that there is a probability of an erroneous setting in a switch.